Apparatus for and method of packaging with gas flushing

ABSTRACT

Upper and lower web portions of sealable material are continuously fed and guided, while products which are to be packaged are delivered in longitudinally spaced relationship therebetween. There is skip-sealing means for sealing the web together on at least one side edge while leaving unsealed side gas outlets at regular intervals. Gas injecting means which extends between the webs has a discharge end located a substantial distance downstream of the skip-sealing means, and there is a cross sealer immediately downstream of the outlet end of the gas injecting means. A first set of soft pressure rolls downstream of the cross sealer presses the webs against the product and exhausts gas and air from the side gas outlets, there being a second set of soft pressure rolls between the cross sealer and skip-seal wheel forming a dam against further upstream travel of the gas, to confine the gas travel to a distance equal to less than the length of one package. Downstream of the first set of pressure rolls there is means for sealing the gas outlets, and there is a cut-off knife for transversely severing the packages at the cross seals.

United States Patent 1191 Pratt 1541 APPARATUS FOR AND METHOD or PACKAGING wmr GAS FLUSHING [75] Inventor: Robert H. Pratt, Milwaukee, Wis.

[73'] Assignee: Pratt Manufacturing Corp., Milwaukee, Wis.

[22] Filed: Dec. 20, 1971 [21] Appl. No.: 210,055

Related US. Application Data [63] Continuation-impart of Ser. No. 69,301, Sept. 8,

1970, abandoned.

Primary Examiner-Travis S. McGehee Attorney- -Arthur L. Morsell, Jr. and Curtis B.

MorselLJr.

[ May 29, 1973 [57] ABSTRACT Upper and lower web portions of sealable material are continuously fed and guided, while products which are to be packaged are delivered in longitudinally spaced relationship therebetween. There is skip-sealing means for sealing the web together on at least one side edge while leaving unsealed side gas outlets at regular inter vals. Gas injecting means which extends between the webs has a discharge end located a substantial distance downstream of the skip-sealing means, and there is a cross sealer immediately downstream of the outlet end of the gas injecting means. A first set of soft pressure rolls downstream of the cross sealer presses the webs against the product and exhausts gas and air from the side gas outlets, there being a second set of soft pressure rolls between the cross sealer and skipseal wheel forming a darn against further upstream travel of the gas, to confine the gas travel to a distance equal to less than the length of one package. Downstream of the first set of pressure rolls there is means for sealing the gas outlets, and there is a cut-off knife for transversely severing the packages at the cross seals.

21 Claims, 10 Drawing Figures 7 PATENTEB MAY 2 9 I975 SHEET 1 OF 3 APPARATUS FOR AND METHOD OF PACKAGING WITH GAS FLUSHING This application is a continuation-in-part of application Ser. No. 069,301, filed Sept. 8, I970, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention pertains to the continuous packaging in sealable material, such as transparent film, of perishable items such as meat, cheese, or the like where the shelf life is increased by use of an inert gas which replaces air in the package or to the packaging of disposable items or devices which must be maintained in sterile condition prior to use.

2. Description of the Prior Art Heretofore various types of apparatus have been proposed for gas packing food products such as cheese. Most of the prior apparatuses, however, relate to entubing of the product in a tube of packaging material having a top or bottom fin seal produced by apparatus such as that of the expired Campbell U.S. Pat. No. 2,882,662. With these prior methods the gas has been discharged into the tube a substantial distance downstream of the package former, and has been caused to travel upstream out of the open end of the tube of packaging material. Such an arrangement is typical of the apparatus of the Podlesak U.S. Pat. No. 2,919,990, and the arrangement of the expired Maxfield U.S. Pat. No. 2,160,367 is similar to that of Podlesak except that, in Maxfield, the gas tube is shorter and the gas travels the length of a single package only. Likewise in the Gerlach U.S. Pat. No. 3,009,298 the gas injection nozzle extends a substantial distance downstream from the former and is caused to react on blocks of food material being wrapped in a tube with a continuous bottom fin seal. One of the embodiments of the Maxfield patent discloses a package having a single side seal, but in this patent there is a complicated former tube or mandrel having a special duct arrangement therein for admitting and exhausting the preservative gas. All of these prior patents exhaust the gas from the open end of the tube being formed.

SUMMARY OF THE INVENTION The present invention provides a novel apparatus and method for gas-packaging items in a package having longitudinal edge portions, usually at one or both sides of the package, which are to be sealed together, wherein there is simple means for controlling the exhaust of air and gas from longitudinally spaced, temporarily unsealed lengths of said edge portions.

A further object of the invention is to provide, as a preferred embodiment, a novel method of packaging products in packages having heat seals along both sides wherein longitudinally spaced, temporarily unsealed gas outlets are employed along both sides.

A further object of the invention is to provide improved apparatus for effecting commercial exploitation of the improved method.

A further object of the invention is to provide a method and apparatus which replaces air in the package with a gas while pressing the packaging material against the product and while providing a simple way of exhausting air and gas.

A further object of the invention is to provide an improved apparatus for packaging products which is relatively inexpensive to construct, which is efficient in operation, and which is well adapted for the purposes described.

With the above and other objects in view, the invention consists of the improved apparatus for and method of packaging products, and all of its parts, combinations, and steps, as set forth in the claims, and all equivalents thereof.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, illustrating one complete embodiment of apparatus for carrying out the invention:

FIG. 1 is a plan view, partially diagrammatic, of the apparatus;

FIG. 2 is an edge view thereof;

FIG. 3 is a transverse sectional view showing a modification;

FIG. 4 is a fragmentary view similar to part of FIG. 2 showing another modification;

FIG. 5 is a fragmentary plan view, partially diagrammatic, showing still another modification;

FIG. 6 is an edge view of the modification of FIG. 5;

FIG. 7 is an edge elevational view of still another modification;

FIG. 8 is a fragmentary plan view showing part of the modification of FIG. 7;

FIG. 9 is a fragmentary plan view of an edge of the web showing the type of seal produced by the modification of FIGS. 7 and 8; and

FIG. 10 is a fragmentary elevational view showing the sealing members of the form of the invention of FIGS. 7 and 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to FIGS. 1 and 2 of the drawings, the numeral 10 designates a suitable conveyor for continuously advancing items 11 which are to be packaged. The items 11 may be cheese, sliced meat, or other material, or may be disposable items or devices which must be kept sterile prior to use, and are preferably of the type that can be packaged in a relatively flat package having one or more longitudinal seals, which seals are usually at the sides of the package. Webs of suitable heat-sealable packaging material 12 are fed from a suitable source of supply into a former 13 of the type shown more particularly in FIG. 4 of U.S. Pat. No. 2,982,066 and having an outlet slot 14. While the drawing illustrates two separate webs being fed into a former of the type illustrated, which webs must be sealed on both sides, it is to be understood that the invention can be carried out as shown in FIG. 3 where a single web has a fold 40 along one side and where sealing has to be done only on the opposite side of the package. The packaging material may be a thin sheet of polypropylene or polyethylene which is inherently heat-sealable, but it may be some other material locally coated with polypropylene or other sealable material or material having areas sealable by pressure either with or without heat.

Extending into'opposite sides of the former from a suitable source of an inert or other gas under pressure, of a type which is useful in increasing the shelf life of food products, such as nitrogen or CO or of a type which is adapted to sterilize items or devices, such as ethylene oxide gas, are gas tubes 15 which are bent to extend longitudinally of the traveling web, and are located between the product and the sides of the package, as illustrated in FIG. 1. The discharge ends 16 of the gas tubes are a substantial distance downstream from the former. Immediately downstream of the former are upper and lower side skip-seal wheels 17, engageable with the web at one side of the packages being formed and, in the preferred embodiment, upper and lower side skip-seal wheels 18 engageable with the web at the other side. These wheels are supported on upper and lower shafts 19 and 20 which are suitably journaled. In the preferred embodiment the wheels 17 and 18 are suitably heated in any well-known manner to perform such heat sealing. Where certain other types of material are used for the webs heat sealing may not always be necessary. As a novel feature of the present invention the sealing wheels 17 and 18 are formed with peripheral cutouts 21 which are 180 apart on each wheel. As the webs advance, the heat sealing wheels 17 and 18 heat seal the side edges of the package as at 22, but at regularly spaced intervals the cut-outs 21 in the heat sealing wheels leave temporarily unsealed gas discharge outlet openings 23. The diameter of the skipsealing wheels 17 and 18 is such that there is an unsealed gas discharge outlet 23 on each side for each package length (referring to the length of the packages 26). The diameters of the skip-sealing wheels 17 and 18 and the location of the cut-outs 21 are such as to provide the gas outlets near the trailing end of the product in each package. This allows the gas to be forced along the product 11 to act on all portions thereof before it reaches the gas outlets.

Between the discharge ends 16 of the gas tubes and the side skip-seal wheels 17 and 18 is a first pair of soft rolls 24 which serve to press the web material against the packaged product 11. These soft rolls 24 also form a dam against the movement of gas or air any further upstream. A second set of soft rolls 25 are suitably supported for rotation above and below the web downstream of the first set of rolls. The spacing between the sets of rolls 23 and 24 is slightly less than the length of one of the completed packages 26 and slightly less than the spacing between cross seals 29.

Positioned midway between the sets of rolls 24 and 25 are upper and lower cross sealing bars 27. These are suitably supported for intermittent movement into cross sealing relationship, and are suitably equipped with heating elements 28 to form the cross seals 29 between packages. One method of operating cross sealing bars is disclosed in FIG. 11 of Thompson U.S. Pat. No. 2,982,066.

Downstream of the soft rollers 25 are additional sets of side sealing wheels 30 and 31. These wheels have only short peripheral suitably heated sealing portions 32 which are 180 apart. The wheels are suitably supported on cross shafts 33 and 34 and are driven in suitably timed relationship so that the peripheral projections 32 engage opposite sides of the packaging material at the unsealed gas discharge openings 23 to seal said portions. Thereafter the packages may pass through a pair of suitably driven pull rolls 3S, and downstream thereof are upper and lower cut-off knives 36 of any well-known type such as those shown in FIGS. 17 to 21 of U.S. Pat. No. 2,982,066, which will act to intermittently engage the transversely sealed portions 29 to sever the packages 26 one from another.

In carrying out the method with the improved apparatus, the material 11 which is to be packaged is fed in spaced relationship in line formation into the former 13 between the moving webs 12. The upper and lower webs are heat sealed at the sides by the side skip-seal wheels 17 and 18 leaving side gas discharge openings 23. Gas which is being continuously discharged from the ends 16 of the gas tubes is always confined between the sets of soft rollers 23 and 24, as the rollers 24 serve as a dam to prevent upstream movement of the gas any further toward the open end of the tube of packaging material. At the same time the soft rollers 25 are continuously pressing the packaging material against the product and causing limited upstream movement of the gas. Inasmuch as this gas, together with the air in the package, is blocked from movement upstream past the rollers 24, it will, whenever a set of side gas discharge openings 23 passes downstream beyond the rollers 24, be discharged from said side outlets 23. As before noted, the side gas outlets are located at the trailing ends of the product 11 within each package portion so that all portions of the product are exposed to the action of the gas before the gas is discharged from the outlets 23. It will be noted from FIG. 1 that the gas outlets 23 which are below the pressing rolls 25 are just in advance of the transverse seal 29 at the end of a package. A limited amount of the inert gas will remain in each package, principally between the borders of the product and the package seals. Thereafter the side seal wheels 30, with the short sealing projections 32, will heat seal the gas discharge openings 23 to completely seal the package. The packages are then severed, one from another, by the cut-off knives 36 as is well known in the art.

In the modification of FIG. 4 the same reference numerals are applied to corresponding parts as are used in FIG. 1 except that the numerals are in a 200 series. Here the only change in construction is in conjunction with the sealing wheels 218 and 218. Instead of having the skip-seal notches 21 of the form of the invention of FIG. 1, the peripheries of the wheels 218 and 218 are continuous. The wheels 218' are mounted on a shaft 220 which shaft is journalled in suitable bearings. The wheels 218 are in continuous contact with the lower web 212. The upper shaft 219 is journalled in bearings 250, one on each side, which are supported on the upper ends of movable supports 251, each support 251 having a large opening 252 through which the shaft 220 for the lower wheels can pass, the opening 252 providing sufficient clearance around the shaft 220 to permit up-and-down movement of the bearing support 251. The lower end of each support 251 has a cam follower roller 252 for coaction with a suitably supported and driven cam 253 having a high portion 254. The upper wheels 218 are the sealing wheels and are heated by any suitable heating means such as the electric heating elements 255.

In use of this modification of FIG. 4 the operation is the same as heretofore described in connection with FIG. 1 except that the unsealed gas discharge openings which correspond to the openings 23 of FIG. 1 are produced by having the high portions of the cams 254 so timed as to cause the upper heated sealing wheels 218 to be temporarily raised out of contact with the upper web 212, at regular intervals and for a sufficient length of time to produce gas discharge openings corresponding to the gas discharge openings 23 of FIG. 1, and located in the same manner relative to the package being formed. Thus the timing in the apparatus of FIG. 1 is such that one set of gas discharge openings such as the openings 23 of FIG. 1 is produced on each side for each package length, and these outlet openings are preferably near the trailing end of the product in each package, as heretofore illustrated and described in connection with FIG. 1. This allows the gas to be forced along the product 211 to act on all portions thereof before the gas reaches the gas outlets at the sides of the package. All of the mechanism after the sealing wheels of FIG. 4 is the same as has been illustrated in FIGS. 1 and 2, including the use of wheels such as the wheels 31 having short sealing portions such as the sealing portions 32 of FIG. 2 for engagement with opposite sides of the packaging material at the unsealed gas discharge openings to finally seal said openings.

In the modification of FIGS. 5 and 6 all of the cone sponding parts are designated by the same numerals used in FIGS. 1 and 2 except that they are in a 3110 series. In this form of the invention, instead of the sealing wheels used in the form of the invention of FIGS. 1 and 2, there are continuously surfaced pressure wheels 318 which are not heated but which apply sealing pressure after the material has been heated by shoe heaters 360. The lower shoe heater on each side is mounted on one end of a lever 361 which pivots with a suitably journaled rock shaft 362. The levers 361 project beyond the shaft 362 and carry cam follower rollers 363 which coact with suitably-supported and driven cams 364. Also mounted fast on the shaft 362 are gears 365.

Each upper shoe 360 is mounted on the forward end of a lever 366, the latter being rigidly secured to a suitably supported upper rock shaft 367, said shaft having gears 368 rigid thereon and meshing with the lower gears 365. Suitably supported springs 369 normally exert an upward pull on the ends of the levers 366.

In the form of the invention of FIGS. 5 and 6, after the web portions 312 leave the former 313, both side edges are acted upon by the heated sealing shoes 360 which are normally together and in sealing position. However, whenever the high portions of the cams 364 engage the cam followers 363, the shoes 360 are temporarily separated, as shown in FIG. 6, to produce unsealed side gas discharge outlets positioned like the outlets 23 of the form of the invention of FIGS. 1 and 2. As soon as the high spots of the cams 364 leave the followers 363, the pull-up springs 369 urge the upper shoes 360 downwardly and, because of the geared arrangement, the lower shoes 360 are moved upwardly. Preferably the shoes 360 are so located as to provide side unsealed gas outlets near the trailing end of the product 311 in each package, just as has heretofore been illustrated and described at 23in connection with the form of the invention of FIGS. 1 and 2. This allows the gas to be forced along the product 311 to act on all portions thereof before it leaves the side gas outlets. The pressure wheels 318 apply the sealing pressure after the material has been heated by the shoe heaters, but there will be no sealing on those portions of the web which had been unheated due to the skip-sealing action of the shoes 360, as shown in FIG. 6.

After the web material leaves the pressure wheels 318 it is acted upon by soft rollers such as the soft rollers 24 of FIGS. 1 and 2 and by all of the other instrumentalities illustrated and heretofore described in connection with FIGS. 1 and 2, including the use of wheels like the wheels 31 of FIGS. 1 and 2 having the short heated sealing portions, like the portions 32 of FIGS. 1 and 2, positioned to engage opposite sides of the packaging material at the unsealed gas discharge openings, such as the openings 23 of FIGS. 1 and 2, to seal said openings.

In the modification of FIGS. 7-10, inclusive, all parts corresponding to parts of the form of the invention of FIG. 1 are designated by the same reference numerals which are, however, in a 400 series, and will not be again described. Here the sealing wheels 418 each have a periphery with a skip-seal pattern formed by transverse obliquely extending cuts or grooves 421, as shown more clearly in FIGS. 8 and 10, the grooves of the upper wheels registering with the grooves of the lower wheels when in the position of FIG. 10. One or both of these wheels is suitably heated in any wellknown manner to perform heat sealing, but wherever the transverse grooves 421 meet, as shown in FIG. 10, there will be skip-sealing to produce a plurality of gas discharge outlets 423 on each side of the package, as shown in FIGS. 8 and 9, which, of course, will be regularly spaced throughout the length of the package. After leaving the wheels 418 with the skip-seal pattern, the packages are acted upon in the same way as heretofore described in connection with the form of the invention of FIGS. 1 and 2, except that, in lieu of the final side sealing wheels 31 of FIGS. 1 and 2, there are wheels 431 which are suitably heated to provide a continuous seal for the purpose of closing the gas discharge openings 423.

The present invention makes it particularly easy to treat perishable products with a gas while the products are being packaged with one or more longitudinal seals. While the preferred embodiments of the invention discloses upper and lower web portions 12 which are originally separate and which must be sealed on both sides, it is obvious that the invention is applicable to similar packages formed from web material where the upper and lower web portions 112 are integral and folded into superimposed position along one side of the package as at 40 in FIG. 3, this type of package requiring only one side seal produced by skip-sealing wheels 117 having cut-outs 121. In this embodiment the gas discharge openings would be along one side of the package only and only one set of side sealing wheels, such as the wheels 30 of FIG. 1, would be required. While an important use of the present invention is in the packaging of perishable products such as food products, the invention also has important utility in connection with the packaging of disposable items or devices which must be maintained in sterile condition in the packages and prior to use. Examples of such items are surgical pads and sponges and other disposable items used by physicians and surgeons. When such items are being packaged, the gas which is injected by the tubes 15 is a suitable sterilizing gas such as ethylene oxide.

It is to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

What I claim is:

1. In packaging apparatus having means for continuously advancing web portions of sealable packaging material, having means for feeding goods in longitudinally spaced relationship between said web portions, having means for continuously forming the packaging material into an elongated tube having at least one set of longitudinal edges which must be longitudinally sealed together, the improvement comprising skip sealing means for sealing said edges while leaving unsealed gas outlets at longitudinally spaced intervals, a gas injecting tube extending into the elongated tube and having a discharge end located a substantial distance downstream of the skip sealing means, a cross sealer downstream of the discharge end of the gas injecting tube, longitudinally spaced transversely extending pressing means continuously engageable with the web portions in longitudinally spaced transverse locations, one of which is downstream of the discharge end of the gas injecting tube and the other of which is upstream thereof to form a dam against upstream travel of the gas whereby it is exhausted from an unsealed gas outlet, and means downstream of said pressing means for sealing said gas outlets.

2. Packaging apparatus as claimed in claim 1 in which the set of longitudinal edges which must be sealed together is at a side of the advancing web portions and in which the skip sealing means is located at said side.

3. Packaging apparatus as claimed in claim 1 in which the pressing means comprises longitudinally spaced transversely extending sets of pressure rolls.

4. Apparatus as claimed in claim 1 in which there is an upper and lower web portion which must be longitudinally sealed together on opposite sides, and in which there is skip sealing means on both sides of the web portions.

5. Packaging apparatus as claimed in claim 1 in which the skip sealing means is a pair of heat sealing wheels having peripheral cutouts.

6. Apparatus as claimed in claim 4 in which there is a pair of heat sealing wheels engageable with each side of the advancing web portions, each pair of wheels having peripheral cutouts.

7. Apparatus as claimed in claim 1 in which the means for sealing the gas outlets comprises a pair of sealing wheels having peripheral projections positioned to engage the unsealed longitudinal edge portions of the webs therebetween.

8. Apparatus as claimed in claim 4 in which the means for sealing the gas outlets comprises a pair of heat sealing wheels on each side of the advancing web portions having peripheral projections positioned to engage the unsealed longitudinal edge portions of the webs therebetween.

9. Apparatus as claimed in claim 1 in which the spacing between the pressing means is less than the distance between cross seals.

10. In a method of packaging the steps of continuously advancing web portions of sealable packaging material, feeding goods in longitudinally spaced relationship between said web portions, continuously forming the packaging material into an elongated tube having at least one set of longitudinal edges which must be longitudinally sealed together, sealing said edges while leaving temporarily unsealed gas outlets at longitudinally spaced intervals, injecting a gas into the tube at a predetermined location downstream, intermittently cross sealing the tube, pressing the tube against the goods at longitudinally spaced transverse locations one of which is downstream of the place of gas injection and one of which is upstream thereof to form a dam limiting upstream travel of the gas and to cause the gas to be exhaused from the unsealed gas outlets, and thereafter sealing the gas outlets.

11. A method of packaging as claimed in claim 10 in which the cross sealing of the web portions is performed in a location between said two pressing locations and downstream of the place of gas injection.

12. A method of packaging as claimed in claim 10 in which the advancing web portions are arranged so that one forms an upper and one a lower web portion and in which the set of longitudinal edges to be longitudinally sealed together is at a side of the advancing web portions and in which the sealing is performed at said side.

13. A method of packaging as claimed in claim 12 in which there are two sets of longitudinal edges one on each side of the advancing web portions which must be longitudinally sealed together and in which the step of sealing while leaving temporarily unsealed gas outlets at longitudinally spaced intervals is performed on both sides.

14. A method of packaging as claimed in claim 11 which includes the step of transversely severing the packages where they have been cross sealed after the sealing of the gas outlets has been accomplished.

15. Packaging apparatus as claimed in claim 1 in which the skip sealing means includes a pair of sealing wheels, and also includes means for moving at least one of said sealing wheels to an inoperative position at regular intervals to leave the unsealed gas outlets at the longitudinally spaced intervals.

16. Packaging apparatus as claimed in claim 15 in which the means for moving a wheel to inoperative position is cam operated.

17. Packaging apparatus as claimed in claim 1 in which the skip sealing means includes sealing shoes normally in sealing position with said longitudinal edges, and also includes pivotally supported means for moving at least one of said sealing shoes to inoperative position at regular intervals to provide the unsealed gas outlets at longitudinally spaced intervals.

18. Packaging apparatus as claimed in claim 17 in which the means for moving a shoe to inoperative position is cam operated.

19. Packaging apparatus as claimed in claim 17 in which there are upper and lower transverse rock shafts above and below the web portions, in which there are shoe supporting levers supported on said rock shafts, and in which the upper and lower rock shafts are geared to each other to provide for conjoint movement of both the upper and lower shoes into and out of engagement with the web portions.

20. Packaging apparatus as claimed in claim 1 in which the skip sealing means is a pair of heat sealing wheels having a regular skip seal pattern thereon.

21. Packaging apparatus as claimed in claim 1 in which said skip seal pattern comprises spaced, transversely and obliquely extending peripheral grooves. 

1. In packaging apparatus having means for continuously advancing web portions of sealable packaging material, having means for feeding goods in longitudinally spaced relationship between said web portions, having means for continuously forming the packaging material into an elongated tube having at least one set of longitudinal edges which must be longitudinally sealed together, the improvement comprising skip sealing means for sealing said edges while leaving unsealed gas outlets at longitudinally spaced intervals, a gas injecting tube extending into the elongated tube and having a discharge end located a substantial distance downstream of the skip sealing means, a cross sealer downstream of the discharge end of the gas injecting tube, longitudinally spaced transversely extending pressing means continuously engageable with the web portions in longitudinally spaced transverse locations, one of which is downstream of the discharge end of the gas injecting tube and the other of which is upstream thereof to form a dam against upstream travel of the gas whereby it is exhausted from an unsealed gas outlet, and means downstream of said pressing means for sealing said gas outlets.
 2. Packaging apparatus as claimed in claim 1 in which the set of longitudinal edges which must be sealed together is at a side of the advancing web portions and in which the skip sealing means is located at said side.
 3. Packaging apparatus as claimed in claim 1 in which the pressing means comprises longitudinally spaced transversely extending sets of pressure rolls.
 4. Apparatus as claimed in claim 1 in which there is an upper and lower web portion which must be longitudinally sealed together on opposite sides, and in which there is skip sealing means on both sides of the web portions.
 5. Packaging apparatus as claimed in claim 1 in which the skip sealing means is a pair of heat sealing wheels having peripheral cutouts.
 6. Apparatus as claimed in claim 4 in which there is a pair of heat sealing wheels engageable with each side of the advancing web portions, each pair of wheels having peripheral cutouts.
 7. Apparatus as claimed in claim 1 in which the means for sealing the gas outlets comprises a pair of sealing wheels having peripheral projections positioned to engage the unsealed longitudinal edge portions of the webs therebetween.
 8. Apparatus as claimed in claim 4 in which the means for sealing the gas outlets comprises a pair of heat sealing wheels on each side of the advancing web portions having peripheral projections positioned to engage the unsealed longitudinal edge portions of the webs therebetween.
 9. Apparatus as claimed in claim 1 in which the spacing between the pressing means is less than the distance between cross seals.
 10. In a method of packaging the steps of continuously advancing web portions of sealable packaging material, feeding goods in longitudinally spaced relationship between said web portions, continuously forming the packaging material into an elongated tube having at least one set of longitudinal edges which must be longitudinally sealed together, sealing said edges while leaving temporarily unsealed gas outlets at longitudinally spaced intervals, injecting a gas into the tube at a predetermined location downstream, intermittently cross sealing the tube, pressing the tube against the goods at longitudinally spaced transverse locations one of which is downstream of the place of gas injection and one of which is upstream thereof to form a dam limiting upstream travel of the gas and to cause the gas to be exhaused from the unsealed gas outlets, and thereafter sealing the gas outlets.
 11. A method of packaging as claimed in claim 10 in which the cross sealing of the web portions is performed in a location between said two pressing locations and downstream of the place of gas injection.
 12. A method of packaging as claimed in claim 10 in which the advancing web portions are arranged so that one forms an upper and one a lower web portion and in which the set of longitudinal edges to be longitudinally sealed together is at a side of the advancing web portions and in which the sealing is performed at said side.
 13. A method of packaging as claimed in claim 12 in which there are two sets of longitudinal edges one on each side of the advancing web portions which must be longitudinally sealed together and in which the step of sealing while leaving temporarily unsealed gas outlets at longitudinally spaced intervals is performed on both sides.
 14. A method of packaging as claimed in claim 11 which includes the step of transversely severing the packages where they have been cross sealed after the sealing of the gas outlets has been accomplished.
 15. Packaging apparatus as claimed in claim 1 in which the skip sealing means includes a pair of sealing wheels, and also includes means for moving at least one of said sealing wheels to an inoperative position at regular intervals to leave the unsealed gas outlets at the longitudinally spaced intervals.
 16. Packaging apparatus as claimed in claim 15 in which the means for moving a wheel to inoperative position is cam operated.
 17. Packaging apparatus as claimed in claim 1 in which the skip sealing means includes sealing shoes normally in sealing position with said longitudinal edges, and also includes pivotally supported means for moving at least one of said sealing shoes to inoperative position at regular intervals to provide the unsealed gas outlets at longitudinally spaced intervals.
 18. Packaging apparatus as claimed in claim 17 in which the means for moving a shoe to inoperative position is cam operated.
 19. Packaging apparatus as claimed in claim 17 in which there are upper and lower transverse rock shafts above and below the web portions, in which there are shoe supporting levers supported on said rock shafts, and in which the upper and lower rock shafts are geared to each other to provide for conjoint movement of both the upper and lower shoes into and out of engagement with the web portions.
 20. Packaging apparatus as claimed in claim 1 in which the skip sealing meAns is a pair of heat sealing wheels having a regular skip seal pattern thereon.
 21. Packaging apparatus as claimed in claim 1 in which said skip seal pattern comprises spaced, transversely and obliquely extending peripheral grooves. 